In the semiconductor industry, fuse elements are widely used features in integrated circuits for a variety of purposes, such as improving manufacturing yields or customizing generic integrated circuits. For example, by replacing defective circuits on chips with redundant circuits on the same chips, manufacturing yields can be significantly increased. A fuse disconnected by a laser beam is referred to as a laser fuse, while a fuse disconnected by passing an electrical current, or blowing, is referred to as an electrical fuse, or e-fuse. By selectively blowing fuses within an integrated circuit that has multiple potential uses, a generic integrated circuit design may be economically manufactured and adapted to a variety of custom uses.
Typically, fuses are incorporated in the design of integrated circuits, wherein the fuses are selectively blown, for example, by passing an electrical current of a sufficient magnitude to cause electro-migration or melting, thereby creating a more resistive path or an open circuit. Alternatively, a current that is weaker than the current required to entirely blow the fuse can be applied to the fuse in order to degrade the fuse, thus increasing the resistance of the fuse. The process of selectively blowing or degrading fuses is often referred to as “programming”.
Conventional fuses are often formed of narrow polysilicon lines or metal lines. In order to reduce the programming currents, the fuses are preferably made as narrow (and thin) as possible. The reduced dimensions of the fuses can tend to increase variation in the programming currents between fuses because the effect of dimensional variations in the fabrication process becomes relatively larger as the size of the fuses decreases. Further, the grain sizes and structures in the polysilicon fuses also affect the programming currents of polysilicon fuses. As a result, the programming currents of conventional fuses may vary over a wide range.
Further, conventional current-programmed fuses suffer from inadvertent programming caused by electro-static discharge currents, which may reach a very high level in a short period of time. New electrical fuses are thus needed to solve the above-discussed problems.